I don’t remember what I did for my plancks but you can just buy standoffs on Amazon or pretty much any keyboard build site. I would just buy a medium sized set of them. In regards to stabilizers and stuff, pretty much any custom keyboard site will have them in stock. Like this one. https://cannonkeys.com/products/aeboards-staebies
Just search on different keyboard forums or discords to find out where people are buying stuff.